1. Field of the Invention
The present invention relates to a method of blowing a synthetic resin into a furnace and an apparatus therefor.
2. Description of the Related Art
The quantity of waste synthetic resins such as plastics as industrial waste and general garbage has recently been increasing, and disposal thereof has become an important social issue. Particularly, plastics, which is a macromolecular hydrocarbon compound, produces a high calorific value during combustion, and cannot be disposed of in a large quantity because of damage to an incinerator upon incineration, so that it is the current practice to dump most of waste plastics onto a reclamation site for waste. However, the dumping of plastics is not desirable from the environmental point view, and there is an increasing demand for development of a quantity disposing method thereof.
Under such circumstances, methods using synthetic resins such as plastics as an auxiliary fuel for blast furnace are disclosed in European Unexamined Patent Publication No. 0622465A1 and Japanese Patent Publication No. S51-33493. These methods comprise blowing milled synthetic resins as a fuel into a blast furnace through tuyeres: the former method, for example, sets forth substantial conditions of the milled synthetic resin to be blown into the furnace including a particle diameter within a range of from 1 to 10 mm and a bulk density of at least 0.35.
As a result of repeated experiments and studies, however, the present inventors found the existence of the following problems involved in the use of synthetic resins such as plastics (hereinafter the description will be based on "plastics" as a typical example) as a blown fuel for a blast furnace.
Plastics rejected as industrial waste or general garbage, when viewed in terms of form, are broadly divided into lumpy plastics taking a plate shape in general and film-shaped ones. The latter ones, film-shaped plastics, account for a considerable part among rejected plastics. However, because of very low transferability and fluidity of milled film-shaped plastics, there is a serious problem in handling when using them as a fuel. More specifically, when blowing plastics into a blast furnace as a fuel, it is the usual practice to cut plastics stored in a storage silo and pneumatically feed cut plastics into the blast furnace. Because of a very low fluidity of film-shaped plastics, milled plastics containing much film-shaped plastics easily produce bridges (scaffolding) in the storage silo, and any problems involving inability to cut out milled plastics in a constant quantity from the storage silo occur frequently. Further, film-shaped plastics clog the cutting port of the storage silo or the interior of a pneumatic feed pipe (particularly at bends and proximity of valves), leading to a serious problem of frequent occurrence of any problems preventing pneumatic feed to the blast furnace.
Unless these problems are overcome, therefore, it is practically impossible to use film-shaped plastics as a fuel to be blown into a blast furnace or the like. In view of the present circumstances of film-shaped plastics accounting for a major portion of waste plastics as a whole, it is clear that advantages of quantity disposal and effective utilization of waste plastics would be lost unless it is made possible to use film-shaped plastics.
In order to blow plastics as a fuel into the blast furnace, furthermore, it is necessary to use milled plastics to ensure a sufficient combustion property. There is however a limitation on the particle diameter acceptable for milling in terms of treatment cost. A particle diameter within a range of from about 1 to 10 mm is therefore a limit for granulation as is shown in the conventional art. When using lumpy plastics milled to this particle diameter, a sufficient combustion property may be unavailable within the blast furnace. As a result, unburned plastics adhere to each other in the bed coke, thus seriously impairing permeability through the furnace, and may cause trouble in the blast furnace operation.
Milled lumpy plastics take an irregular and angular shape. Ones having a particle diameter of from 1 to 10 mm are therefore low in discharge property upon cutting out from a storage silo and in fluidity and transferability when pneumatically feeding to the blast furnace, leading to easy occurrence of clogging at the cutting port of silo or in the middle of the pneumatic feed pipe system.
It is therefore very difficult to use waste plastics as a fuel to be blown into a blast furnace in an industrial scale by any of the methods proposed by the conventional arts: simply milling plastics into a particle diameter of from 1 to 10 mm processing the same into granules having a high bulk density and blowing the same into the blast furnace.